The present invention relates to a process for preparing legumes exhibiting reduced flatulence when digested by mammals and a process for reducing flatulence in legumes when digested by mammals and the products thus prepared.
Legumes are important foodstuffs and are likely to become more so in the future. For example, many legumes, especially those in some of the legume genuses, such as Phaseolus, Soja and Lens, are high in protein and provide an inexpensive alternative to animal protein.
Unfortunately, ingestion of some of the most nutritious and abundant legumes can be accompanied by severe flatulence as well as abdominal distress and poor digestibility. More specifically, the flatulence results in discomfort, diarrhea, loss of appetite, and poor growth, all of which have prevented the wide-scale use of these vegetable nutrients.
It is believed that the flatulence is due to various factors. For example, it has been postulated that the flatulence is attributable to the indigestibility by mammalian digestive enzymes of the flatulence-causing alpha oligosaccharides, such as raffinose, stachyose, and verbascose, and the like, present in legume products. The generally accepted explanation of the action of the alpha oligosaccharides in producing flatulence is that the enzyme alpha galactosidase, which hydrolyzes the xcex1-oligosaccharides, is not present in the intestinal tract of mammals. Thus, these compounds are not hydrolyzed and dissolved in the digestive tract so that they can be absorbed. Instead, they reach the lower intestine essentially intact. Here, anaerobic bacteria ferment these sugars with the resultant production of carbon dioxide, hydrogen, and methane gases, thereby producing flatus.
However, these xcex1-oligosaccharides are believed not to be the only source present in the legume that causes flatulence. It has been reported that flatulence is also due to components present in the cell wall fiber constituents. Other have conjectured that, besides the galactose-containing oligosaccharides, undigested starch and protein in the legumes are contributing factors to flatus production.
Various solutions have been proposed to reduce flatulence in legumes, but many of these focus on just one of the factors described hereinabove, viz., the flatulence-causing oligosaccharides and not on enhancing the digestion of the starch in the legume. It has been suggested by researchers, however, that, at least with beans, oligosaccharides account for only about ⅓ of the cause of flatulence, and that ⅔ is caused by other components such as, e.g., undigested starch in the bean. Other research indirectly suggests that the sugars are responsible for the violent xe2x80x9cepisodesxe2x80x9d that occur approximately within five hours after ingestion of the legume, while xe2x80x9cbackground flatulencexe2x80x9d, which occurs regularly over a six to eight hour period after eating, is caused by the non-digested starch. Unfortunately, very little research, in comparison, has been directed to reducing the flatulence caused by these other components.
Recently, Yansoo Chung, in his Ph.D. thesis from Michigan State University (1996), reported that cooking whole navy beans for 10 minutes caused starch crystallization within the cell wall of the navy beans, thus impeding and preventing the digestive enzymes in the stomach from digesting (hydrolyzing) the starch.
Therefore, based upon these findings additional investigations are required to find the appropriate conditions to prevent such crystallization from occurring and thereby enhance the digestibility of these starches in the bean.
However, the present inventors have found a means to effectively reduce the flatulence caused from the undigestible starch in the legume.
The present invention is directed to a process for maximizing starch gelation in a legume when digested by mammals, which process comprises:
(1) soaking a legume in a water bath in stagnant, sprayed or flowing water at a first temperature which is at or above ambient temperature but less than the first critical rehydration temperature, under conditions effective and for a period of time sufficient to produce a rehydrated legume having a moisture content which is at least 50% of that of a fully hydrated legume but less than a fully hydrated legume;
(2) heating the product of step (1) in a water bath to a second temperature under conditions effective to increase the moisture content to an amount which is greater than that of full hydration; said second temperature being greater than the first critical rehydration temperature and at about or greater than the endogenous oligosaccharide-reducing enzyme inactivation temperature and less than the maximum temperature of starch gelation; and
(3) optionally blanching the product of step (2) at blanching effective temperatures, said blanching temperature being greater than the first and second temperatures.
The present invention is also directed to the preparation of a legume exhibiting reduced flatulence when digested by a mammal, which comprises repeating steps (1)-(3) hereinabove, and then
(4) mixing the legume thus treated with a food acceptable vehicle to form a legume-based mixture; and
(5) treating the product of step (5) under the desired preservation methods.
The present invention is also directed to the product thus formed by the processes described hereinabove.
In another embodiment of the present invention, the legumes are prepared by the above process with an additional step between steps 1 and 2. More specifically, the product of step (1) is first heated in a soak water bath at a transition temperature which is greater than the first temperature but less than the second temperature.
In still another embodiment of the present process, the soak water is fully or partially drained and replaced and fresh water is simultaneously added or bled in during the full or partial drain; this may occur after or even during any of the steps enumerated hereinabove at a rate sufficient to maintain a positive oligosaccharide driving force at a level that minimizes cracking for a time sufficient to reduce the brix of the soak water. This step can be repeated any number of times.
In another embodiment of the present invention, after the second step of the process but prior to blanching, the temperature of the soak water bath is optionally lowered to a third temperature until the oligosaccharide content of the legume is lowered to a desired level.
In another embodiment, an aqueous solution of a food grade calcium sequestering agent, such as a phosphate salt is added to the soak water at a concentration and for a time sufficient to soften the legumes as desired. The calcium sequestering agent can be added to the soak water at any step in the process.